High vacuum vapor jet pump



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u. LAMM HIGH VACUUM VAPOR JET PUMP Flled Jan 18, 1939 March 12, 1940.

Patented Mar. 12 194 HIGH VACUUM VAPQEE, PUMP "Uno Lamm, Ludvika, Sweden, Allmanna Svenska Elektrisha a corporation of Sweden Vasteras, Sweden,

assigner to Aktiebollaget,

Application January is, was, Serial N0. 251.4% in Sweden January 22, 1938 7 Claims.

conductivity of the material but also on certain constructive principles such pumps.

generally employed .in Thus for instance, the boiling chamber has been separated from the pump casing and has communicated with the latter by a m-outer rising pipe opening at the top of the pump casing and by a separate down-flow pipe 35 for the condensed vapor.

In designing vapor jet pumps made of metal,

it has hitherto mainly been held in view to obtain a compact structure which can, however, be taken apart for inspection and repair, and

go for this purpose, the boiling chamber has been placed immediately below the pump casing and the rising tube for the vapor inside the latter. Hereby a great leakage of heat directly from the boiling chamber to the pump casing has been caused, and it has been diflicult to insulate the rising tube for the vapor eificiently from the condensing chambers, whereby a considerable leakage of heat has taken place also by this way. The result has been a too large leakage of heat in comparison with the effective power of the pump, said inconvenience being especially prominent in pumps for a small eifective power, for instance such as are employed for keeping vacuum in certain types of rectifier valve vessels of metal, whereby it has been practically impossible to construct such pumps for air cooling, at least for such cooling without a forced draught.

It is highly desirable that it should be pos-. sible to employ a cooling of the last-mentioned type also in vapor jet pumps made of metal. It is, however, not possible simply to copyfthe'formgiving of glass pumps therein, partly with respect to the higher heat conductivity of the metal, partly for constructional and, working reasons.

According to the presentinvention, a high vacuum pump made of metal and having a plurality of vapor jet nozzles operating after each other and situated above each other in a common, cylindrical casing, and to which the vapor-is led through a common supply pipe which is removable upwards as well as the nozzles, is so arranged that the vapor supply pipe leading from above in a manner known in glass pumps is connected, by a detachable joint at the top of tom so as to be able the pump, to a rising pipe for the vapor, arranged externally in a manner also known in glass pumps and leading from a boiling chamber separated from the pump. Hereby the assembling as well as the disassembling of the pump 8 for inspection and repair is facilitated in the most simple manner. It is particularly recommended to introduce the rising pipe for the vapor in a lateral extension of the pump casing at the top thereof.

Two forms of the invention are illustrated in the accompanying drawing, in which Fig. 1 shows the entire pump in a vertical section, while Fig. 2 shows a section of the top of the pump casing.

In'Fig. 1, l is the cylindrical casing of them pump and 2 a lateral extension at the top thereof.

3 is the boiling chamber and d a heating element therefor. The vapor leaves the boiling chamber through the pipe 5 which is heat'insulated externally by the evacuated space between it and the 20 surrounding pipe 6. Both pipes 5 and 6 are welded to the boiling chamber in a vacuum-tight manner. At the top, the pipe 6 is welded to the bottom of the extension 2 at I, while the vapor pipe 5 passes freely through a hole in said bot- 5 to expand and contract freely at variations of temperature. The vapor pipe is, by means of a, coupling 8, detachably connected to the pipe 9 leading to the nozzles.

10, II, and I2, which are only diagrammatically 30 shown in the drawing. They discharge into annular inset pieces 2|, l3, H which form partitions between the suction andpressure sides of the nozzles III, II, l2. These inset pieces may preferably be secured to the casing by a shrinking 35 or swelling. procedure, being in the latter case preferably cooled by liquid air before being mounted in place. i

The gases conveyed and compressed by the pump leave the pump casing together with the 40 condensed vapor by the pipe l5 which conveys them to the liquid seal l6. Here the gases are separated from the liquid and escape through the pipe H to the low vacuum. system, while the condensed liquid returns to the boiling chamber 45 through the pipe I 8-. The liquid seal I6 acts as a back pressure valve when the pump is out of operation. The pump is connected to the evacuated receptacle by a pipe l9 which is joined to the extension 2 by a mercury-sealed joint. The 50 casing is cooled by cooling flanges 20 and generally needs no forced air current for cooling. On account of the vapor pipe 5 being introduced through the extension 2 of the casing, the pipe 9 and the nozzles 10, H, and I! may be removed 66 from the casing unimpeded by the pipe 5 after disassembling. the coupling 8. It is also possible to introduce the inset pieces l3, l4, 2| after the completion oi the weld I which is an advantage in the manufacturing of the pump, as no welding with an accompanying oxidation and slag formation need to be performed on the pump body after the introduction of the said pieces.

Fig. 2 shows a modified detail of the pump casing I with the vapor pipe 5. Also in this form, the vapor pipe is introduced into the easing through a lateral extension thereof. The said extension here consists of a metal tube 30 concentric with the vapor pipe 5. By this arrangement, it is also avoided-that the joint between the vapor pipe and the pump casing forms a barfor the removal of the inner parts, and at the same time the necessary vacuum tight joint between the hot vapor pipe and the cold pump casing is such that the heat transmitting resistance between the, said parts will be large and the heat leakage thus small. The detachable joint between the rising pipe 5 and its continuation 9 is here illustrated as a conical joint 3| in ,0 which the members are pressed together by a spring 32. i

I claim as my invention:

1. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing, vapor jet nozzles arranged above each other in said casing, a common vapor distribution pipe connecting said nozzles and being removable together with these through the top of said'casing, an evaporation chamber separated from said casing, a rising pipe for vapor from said chamber. outside said casing, and a detachable joint externally subjected to the low pressure at the top of said casing and connecting the said rising pipe and said vapor distribution pipe.

2. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing, having a lateral extension at the top, vapor jet nozzles arranged above each other in said casing, a common vapor distribution pipe connecting said nozzles and being removable through the top of said casing, an evaporation chamber separated from said casing, a rising pipe for vapor from saidchamber outside said casing entering said lateral extension, and a detachable joint externally subjected to' the low pressure at the top of said casing and connecting the said rising pipe and said vapor distribution pipe.

3. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing having a cylindrical chamber of larger diameter at the top, vapor jet nozzles arranged above each other in said 'casing, a common vapor distribution. pipe connecting said nozzles and being removable through the top of said casing, an evaporation chamber separated from said casing, a rising pipe for vapor from said chamber outside said casing entering said cylindrical chamber. and a detachable joint externally subjected to the low pressure at the top of said casing and connecting the said rising pipe and said vapor distribution pipe.

4. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing having a lateral extension at the top, vapor jet nozzles arranged above each other in said casing, a common vapor distribution pipe connecting said nozzles and being removable through the topof said casing, an evaporation chamber separated from said casing, a rising pipe for vapor from saidchamber outside said casing entering said lateral extension, a pipe surrounding said rising pipe and communicating with said lateral extension, and a detachable joint between said rising pipe and said vapor distribution pipe at the top of said casing.

5.-A high vacuum vapor jet pump'comprising a vertical cylindrical metal casing having at the top a lateral cylindrical extension forming an angle therewith, vapor jet nozzles arranged above each other in said casing, a common vapor distribution pipe connecting said nozzles and being removable through the top of said casing, an

evaporation chamber separated from said casing, a rising pipe for vapor from said chamber outside said casing entering said lateral cylindrical extension, a solid heat insulation surrounding said rising pipe, and a detachable joint between said rising pipe and said vapor distribution pipe .at the top of said casing.

6. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing, vapor jet nozzles arranged above each other in said casing, annular pieces adjacent to said nozzles secured inside said cylindrical casing by thermal expansion, a common vapor distribution pipe connecting said nozzles and being removable through the top of said casing, an evaporation chamber separated from said casing, a rising pipe for vapor from said chamber outside said casing, and a detachable joint between said rising pipe and said vapor distribution pipe at the top of said casing.

"I. A high vacuum vapor jet pump comprising a vertical cylindrical metal casing having a lateral extension at the top, vapor jet nozzles arranged above each other in said casing, a common vapor distribution pipe connecting said nozzles and being removable therewith through the top of said casing, an evaporation chamber separated from said casing, a rising pipe for vapor from said chamberoutside said casing and entering said lateral extension, and a detachable joint between said distribution pipe and said rising pipe arranged laterally with respect to the interior of said casing so as to permit the tree removal of the detachable contents thereof.

0 LAMM. 

